VI PREFACE. 



the systems more familiar to English students. In any rearrange- 

 ment much of the significance of Dr. Warming's valuable and 

 original observations would have been lost, and also from a 

 teacher's point of view I have found this system of great value. 

 Although at present it may not be completely satisfactory, yet as 

 an attempt to explain the mutual relationships, development and 

 retrogression of many of the orders, it may be considered to have 

 a distinct advantage over the more artificial systems founded 

 upon Jussieu's Divisions of Polypetalae, Gainopetalse, and 

 Apetalae. 



With reference to the principles of the systematic arrangement 

 adopted, I may here insert the following brief communication 

 from the author (dated March, 1890), which he has requested me 

 to quote from the preface of Dr. Knoblauch's edition : " Each 

 form which, on comparative morphological considerations, is 

 clearly less simple, or can be shown to have arisen by reduction 

 or through abortion of another type having the same fundamental 

 structure, or in which a further differentiation and division of 

 labour is found, will be regarded as younger, and as far as 

 possible, and so far as other considerations will admit, will be 

 reviewed later than the ' simpler,' more complete, or richer forms. 

 For instance, to serve as an illustration : EPIGYNY and PERIGYNY 

 are less simple than HYPOGNY ; the Epigynous Sympetalse, Chori- 

 petalse, Monoctyledones are, therefore, treated last, the Hydro- 

 charitacecK are considered last under the Helobiece, etc. ZYGOMORPHY 

 is younger than ACTINOMORPHY ; the Scitaminece and Gynandrce 

 therefore follow after the Liliiflorce, the Scrophulariacece after the 

 Solanacece, Linaria after Verbascum, etc. FORMS WITH UNITED LEAVES 

 indicate younger types than those with free leaves ; hence the 

 Sympetalce come after the Choripetalse, the Silenece after the 

 Alsinese, the Malvacese after the Sterculiacese and Tiliacece, etc. 



"ACYCLIC (spiral-leaved) flowers are older than cyclic (verticillate- 

 leaved) with a definite number, comparing, of course, only those 

 with the same fundamental structure. The Feromca-type must 

 be considered as younger, for example, than Digitalis and Antir- 



